A boost converter is a power converter with an output DC voltage greater than its input DC voltage. This type of circuit is used to “step-up” a source voltage to a higher, regulated voltage, allowing one power supply to provide different driving voltages.
As shown in FIG. 1, an example of conventional boost converter uses an inductor 2 as an energy storage component, the charging and discharging of which are controlled by a power switch 6 and a diode 4. Sometimes a capacitor connects the output terminal 5 and the ground to supply a steady output voltage. A potential problem with using such a boost converter in FIG. 1 is that the converter cannot be truly shut down which makes for large power consumption when the converter is in standby mode. Moreover, the boost converter in FIG. 1 is not short circuit proof, because there is inherently no switch-off device in the short circuit path. In particular, once the output terminal 5 is short connected, current from the input terminal 1 to the output terminal 5 will rise uncontrollably and may damage the circuit components (the diode 5, for example).
A known solution for the problem of shutdown is shown in FIG. 2 and consists of providing a load switch 7 between the diode 4 and the output terminal 5. When the converter needs to be shut down, the power switch 6 and the load switch 7 are opened and the input terminal 1 is isolated from the output terminal 5.
However, the boost converter in FIG. 2 still has the problem of short circuit. In detail, current may rise to a remarkable level within micro-seconds, for example, and damage circuit components when a short circuit event happens. To prevent this condition, the load switch 7 should be opened immediately. However it is not feasible for the boost converter in FIG. 2 to do so because the load switch 7 should be closed for a period long enough to safely remove the current energy stored in the inductor 2 prior to shutting down of the converter, otherwise the energy of the inductor 2 can cause the voltage at node 8 to rise to a high level which can damage devices connected to the node 8.
Thus there is a need for a circuit and method providing both short circuit protection and energy removal.